Actuators, for example window operating actuators and actuators for operating a sliding roof, are already known. They have a gear unit and a motor unit. The gear unit has a worm wheel and a gear shaft implemented as a worm shaft. The motor unit consists of a motor housing, a brush housing, and an internally located rotor. The rotor is therein embodied as what is termed a laminated rotor core having a plurality of lamella segments secured on the motor shaft. The gear shaft and motor shaft can also be embodied as a single piece forming a common drive shaft. The motor housing is flange-mounted onto the gear housing when the actuator is assembled. A mostly cylindrical extension of the brush housing protrudes with the drive shaft and the worm shaft located on the drive shaft's free end into a corresponding opening in the gear housing. The extension of the brush housing serves as a support for a bearing in which the drive shaft is ducted. The cylindrical extension can also be embodied as a separate bearing housing or, alternatively, can form a common brush and bearing housing with the brush housing.
An actuator wherein a motor housing is flange-mounted onto a gear housing is known from EP 0 869 295 A2. The motor housing protrudes partly into an opening in the gear housing, with the protruding part enclosing a cap bearing in which is ducted a motor shaft.
The bearing located opposite the gear and housed in the cylindrical bearing housing serves as a compensating element for compensating manufacturing tolerances when the actuator is assembled. The bearing is therein to some extent moveable axially in its support. If the bearing is a cap having a spherical outer surface able to move within certain limits in a spherical shell corresponding thereto of the bearing support, then it will also be possible to compensate warps in the drive shaft and radial displacements thereof. Pretensioning is applied to said bearing so that it will remain fixed in its position after assembly.
A frequent problem is that the bearing inserted along with the cylindrical bearing housing into the opening in the gear housing becomes loose after a certain period of operation and that, in the case of a cap, this can twist in its bearing shell. This is caused by settling processes to which plastics are subject when under a permanent load. Pretensioning that is still present in the new condition will be reduced thereby in such a way that the bearing or, as the case may be, the cap will over time begin to work loose in the bearing support. This results in wear and tear on the bearing or, as the case may be, cap and hence in premature failure of the actuator. Increasingly more noise is also produced when the actuator is operated.
To resolve the problem it is known how to employ what is termed a clamping collar, made of spring steel, which exerts a clamping force on the bearing or, as the case may be, the spherical outer surface of the cap. A permanent frictional force is exerted thereby between the gear housing and the bearing housing so that non-twisting and axial securing of the bearing are achieved. What is disadvantageous about this solution are the increased component requirements and the assembly effort required.